Applicant has previously discovered and isolated an agent from bone tissue capable of inducing bone formation when implanted in tissue cells. The inductive agent has been named bone morphogenetic protein, designated BMP. See, U.S. Pat. No. 4,294,753; U.S. Pat. No. 4,455,256; and pending Application Ser. No. 523,606, filed Aug. 16, 1983, that are incorporated herein by reference.
Applicant also has discovered and produced from bone tissue related inductive agents: bone morphogenetic peptides (BMP-p) and bone morphogenetic protein polypeptide (BMPP). BMP-p are smaller peptides containing the functional and immunoreactive domain of BMP. BMPP is a lower molecular weight bone morphogenetic agent that is believed to be a subunit of BMP.
The biochemical mechanism by which the BMP family of agents induces bone formation is not known. However, the process has been classified as phenotypic transformation, as distinguished from malignant transformation by a carcinogen. Phenotypic transformation is a self-limited host-regulated development process. BMP agents induce bone to develop de novo in extraskeletal sites by differentation of perivascular connective tissue pericytes.
The discovery by applicant of BMP agents heralds a new era in the treatment of many bone disorders. When exogenous BMP was implanted in a fracture, or surgical bone defects, repair of the bone rapidly occurred within a few months. It is expected that BMP-induced de novo synthesis of bone tissue will replace many types of bone transplant operations. Present and future applications of BMP implants cover all forms of bone disorders.
The present invention relates to the diagnosis of bone disorders based upon applicant's discovery that even though BMP had been isolated from bone and classified as a paracrine rather than an endocrine agent, BMP is quantitatively detectable in serum by assay methods such as radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA). Urist, M. R., Hudak, R. T., Radioimmunoassay of Bone Morphogenetic Protein in Serum: A Tissue-Specific Parameter of Bone Metabolism, Pro Soc Exp Biol Med., 176:472-475 (1984). BMP was found in sera of normal adult subjects unimplanted with exogenous BMP. Without intending to be limited by theory, the working hypothesis is that BMP is a normal by-product of bone metabolism, and it now has been found that assaying the concentration of serum BMP or anti-BMP antibody is diagnostic of bone health or disease.
BMP RIA and BMP ELISA values were higher in rapidly growing children with normally high levels of bone turnover than in non-growing adults with normally low rates of bone turnover. Patients with extensive Paget's disease showed very high levels of serum BMP. The range of BMP values in patients with osteosarcoma was about the same as observed in rapidly growing children. Women with osteoporosis had serum BMP mean values that were about 10-11% that in normal premenopausal women. BMP RIA mean values in non-osteoporotic post menopausal women were within the range observed in normal premenopausal women.
Alkaline phosphatase, a ubiquitous enzyme, is the time-honored chemical laboratory indicator of the level of osteoblastic activity. Alkaline phosphatase levels are generally elevated in adults with Paget's disease and some types of osteosarcoma, conditions characterized by increased osteoblastic activity associated with increased bone turnover. In osteoporosis in postmenopausal women, in whom alkaline phosphatase levels are generally normal, the levels of serum BMP were low. Thus in osteoporosis, a disease for which there is no presently known laboratory method of diagnosis, serum BMP determinations were more useful than alkaline phosphatase for early detection of osteoporosis.
Another novel method for diagnosing bone disease also has been developed. Assaying the concentration of anti-BMP antibody in serum, or the ratio of serum BMP:anti-BMP antibody, is diagnostic of bone health or disease.
Based on the present invention, a commercially feasible diagnostic kit for diagnosing bone disorders can be designed comprising means for assaying BMP or anti-BMP antibody in body fluids.